This invention relates to hermetically sealed compressors and, more particularly, to an improved oil pick-up tube for such compressors.
Compressors used in domestic and commercial refrigeration applications generally employ vertically arranged eccentric crank pins having one end connected to the rotor of an electric motor and a crank journal end driving a compressor piston. The compressor has a hermetically sealed housing, which provides a sump for lubricating oil at its lower end. Lubricating oil is conducted from the sump to machine elements requiring lubrication by a pick-up tube usually connected to a passage in the crank journal and extending into the oil sump. Since the crank journal is offset from the rotational axis of the motor, the pick-up tube enters the oil sump at an angle with its distal end intersecting the rotational axis. This arrangement pumps the oil by the centrifugal force created by the offset. However, considerable turbulence and splash noise is created by the angularity of the tube as where it enters the surface of the oil. Examples of slant pick-up tube arrangements may be found in U.S. Pat. Nos. 2,738,919; 3,545,891; 5,377,781; and 5,795,140.
Other slant pick-up tube arrangements employ an oil clip having a longitudinal slit, which is intended to separate the refrigerant from the oil. These arrangements tend to pick up high amounts of refrigerants at the surface of the sump and create considerable noise by oil splashing. Examples of such arrangements may be found in U.S. Pat. Nos. 3,858,685 and 5,085,579.
It is desirable to provide an oil pick-up tube which substantially eliminates oil-splash noise while providing an effective oil pump to deliver lubricating oil to the bearing surfaces of the compressor. It is also desirable to provide an oil pick-up tube which reduces the amount of refrigerant and, therefore, the amount of oil delivered to the bearing surfaces.
This invention relates to an oil pick-up tube which reduces oil splash noise and transient sound emissions while delivering a proper amount of lubricating oil to the bearing surfaces of a compressor.
More specifically, the invention relates to an oil pick-up tube for a hermetically sealed compressor. The compressor comprises a housing defining an oil sump and housing an electric motor. The motor has a stator and a rotor with the rotor connected to one end of a vertically oriented crankshaft. An offset crankshaft journal is provided at the other end of the crankshaft which is received by a connecting rod pinned to a compressor piston. The piston is received in a compressor cylinder. An oil passage is provided in the crankshaft journal and communicates with bearing surfaces in the compressor.
The oil pick-up tube has a first end portion in fluid communication with the oil passage in the crankshaft journal and has a second straight end portion projecting through a surface portion of a body of lubricating oil in the sump. The second straight end portion is axially aligned with the vertical rotation axis of the crankshaft. An S-shaped midportion connects the first and second end portions. The second straight end portion has a helically twisted fin inserted therein with a press fit. Since the second end portion rotates about its own axis, the twisted insert acts as a screw pump to conduct oil through the second end portion to the S-shaped midportion. Centrifugal force caused by the offset of the crankshaft journal pumps oil into the journal and to the bearing surfaces.
Preferably the first end portion of the tube is straight and is inserted in the oil passage of the crankshaft journal with a press fit. A radial flange is provided on the tube to limit the amount of tube inserted in the passage and properly locate the second straight end portion relative to the oil sump.